etaoin shrdlu

the letters produced by running the finger down the first two vertical rows of keys at the left of the keyboard of a Linotype machine: used as a temporary marking slug or to indicate that an earlier mistake in the line necessitates resetting, but sometimes inadvertently cast and printed.

1931, journalism slang, the sequence of characters you get if you sweep your finger down the two left-hand columns of Linotype keys, which is what typesetters did when they bungled a line and had to start it over. It was a signal to cut out the sentence, but it nonetheless sometimes slipped past harried compositors and ended up in print.